Melting ice in the Arctic is making it difficult for the bears to hunt.
Scientists in the report in Nature Climate Change say that polar bears' shrinking body weight is also playing a factor in how the species could survive in the Arctic.
“It also suggests that, with high greenhouse gas emissions, steeply declining reproduction and survival will jeopardize the persistence of all but a few high-Arctic subpopulations by 2100. Moderate emissions mitigation prolongs persistence but is unlikely to prevent some subpopulation extirpations within this century,” the study said.
Due to the Arctic warming faster than the rest of the planet, the scenario for polar bears is particularly dire.
"The Arctic is warming at 3 times the average of the globe because of human-caused climate change ... and as a result the landscape of the Arctic is changing at a staggering pace," CBS News meteorologist and climate specialist Jeff Berardelli said. "We are running out time to limit the damage from climate change. There is no doubt we will forever lose vital species. The question is just how many are we willing to sacrifice? That will be determined by how quickly and boldly we take action to limit climate change and habitat destruction."